Engine governor with fast reference positioning and slow opening and closing movement of throttle limiter

ABSTRACT

An engine governor having overriding means for limiting the flow of fuel to an engine, means for moving the overriding means to an intermediate reference position upon actuation of the governor, and means for moving the overriding means from the reference position to other positions for limiting the flow of fuel to that suitable for operating the engine at speeds close to a set speed. Means for actuating the governor before the engine reaches the set speed, means for moving the overriding means from the reference position to the other limiting positions at a very slow rate, and means for moving the overriding means toward limiting the fuel flow to a minimum when an over-running load causes the engine speed to run a predetermined amount above the set speed. The engine governor may be combined with a load speed governor for independently governing the engine to a speed safe therefor, and to a lower speed safe for the load and may also have a power take-off governing mode which is selected automatically upon connection of the power take-off to the engine.

CROSS-REFERENCE TO RELATED APPLICATION

This is a division of application Ser. No. 471,904, filed Mar. 7, 1983,which is a continuation of U.S. application Ser. No. 168,566, filed July14, 1980, now abandoned, which is a continuation-in-part of U.S.application Ser. No. 30,064, filed July 4, 1979, now abandoned.

BACKGROUND OF THE INVENTION

The background of engine governors in general, and a full disclosure ofmy previous invention in combined engine and load speed governors, iscontained in prior U S. patent application No. 794,615, filed May 6,1977, now U.S. Pat. No. 4,181,103. My aforesaid engine governor was of adynamically-surging type which allowed engine speed to oscillate ratherrapidly (and forcefully for a vehicle in a lower gear ratio) about itspredetermined limit.

While such oscillations are not damaging to the engine and may behelpful in encouraging a truck driver to "get out" of a lower gear ratioand into a higher ratio where the engine will be operating moreefficiently, it is also advantageous to have an engine governor whichallows the engine to be accelerated to its predetermined speed limitwith less overshoot beyond that limit than provided by my previousdynamically-surging governor, and which will thereafter bring the enginequickly to run in close approximation to the predetermined speed limit,wandering from it only perhaps 1% when in a very low gear and less inhigher gears, and that probably not on any cyclical basis. Such actionis obtained basically by positioning the engine throttle to apredetermined reference position upon acceleration of the engine to apredetermined speed and actuation of the engine governor thereby, ratherthan by driving the throttle toward a full-closed position as in theaforesaid U.S. Pat. No. 4,181,103.

Such a smooth and gentle control is advantageous for full economy, andfor driver and/or passenger comfort, especially for an application suchas a school bus engine or a truck engine also used to drive a powertake-off (PTO), and is typical of my present invention which providessuch an engine speed governor and also combines it with a load or roadspeed governor essentially like that of the aforesaid U.S. Pat. No.4,181,103. The present combination functions to safely control engineand load speeds generally like the combination of my aforesaid patentapplication, except smoothly without the previously-experienceddynamic-surging in engine speed control mode. However, when the smoothgoverning is used in a PTO governing mode, the aforementioned surginggoverning may be used therewith in an engine governing mode. The presentinvention includes an overspeed control which acts to close the throttlebeyond the reference position toward a completely closed position in theevent of prolonged speeding outside a normal range above thepredetermined speed limit (as would be possible for a driver proceedingdownhill with the accelerator pedal "floored" or calling for maximumthrottle opening), thereby retaining generally the feature of myprevious invention which acted to close the throttle toward a completelyclosed position whenever the engine speed remained anywhere above thepredetermined limit.

Like my previous invention, the apparatus of the present invention is astandard unit which may be connected to the standard carburetor,ignition system, and speedometer cable of any engine and vehicle, sothat it may be applied at the factory or in the field withoutinconvenience, and spare parts for this apparatus will be the same forany engine-vehicle combination. However, my present invention alsocontemplates the use of a lost-motion type overriding carburetor linkage(in place of the equally useable linkage-lengthening capsule disclosedin my aforesaid patent application) which gives a more conventional feelto the accelerator pedal, but with a more complicated parts situation,since each different engine-carburetor combination may require differentlinkage parts and adaptations. Also, use of a conventional pulsegenerator connected to the tachometer drive of a Diesel engine iscontemplated for application of the apparatus of the present inventionthereto.

SUMMARY OF THE INVENTION

Briefly described, the present invention provides a speed limitinggovernor for use with an engine having a throttle means mechanicallymovable between an open position and a closed position to regulate theflow of energy-supplying means to the engine, the governor includingmeans for sensing the speed of the engine; means adapted to be connectedto the throttle means for selectively overriding the mechanicaloperation thereof, the overriding means being movable in a firstdirection toward a closed throttle position and in a second directiontoward an open throttle position, and being movable to a predeterminedreference position intermediate the open and closed throttle positions;and control means responsive to the speed sensing means for moving theoverriding means in the first direction to the predetermined referenceposition when the engine speed reaches a first preset level. The controlmeans may be responsive to the speed sensing means for moving theoverriding means alternately in the second and first directions when theengine speed is within a preset range after the overriding means reachesthe reference point, and for moving the overriding means away from thereference point in the second direction when the engine speed fallsbelow the preset speed. The control means may be responsive to the speedsensing means for moving the overriding means to the predeterminedreference position and for causing it to cease further movement as longas the engine speed remains within a predetermined speed range above thefirst preset level.

Preferably, the control means may be responsive to the speed sensingmeans for moving the overriding means away from the reference positionin the first direction when the engine speed exceeds a second presetspeed higher than the first preset speed, and for moving the overridingmeans in the first direction to the predetermined reference positionwhen the engine speed accelerates from one speed level to another speedlevel within a predetermined amount of time, the one speed level and theaforesaid another speed level both being below the first preset speedlevel.

A preferable embodiment provides that the control means moves theoverriding means away from the reference point in the second directionat a rate of movement which is slower than the rate of movement of theoverriding means when it moves in the first direction, and theoverriding means may continue moving away from the reference position atthe slower rate of movement until the engine speed again exceeds thefirst preset level or until the overriding means has moved beyond apredetermined reference zone adjacent the reference point, whicheveroccurs first.

A preferred embodiment provides that the control means causes theoverriding means to stop after moving in the second direction beyond thepredetermined reference zone until the engine speed exceeds the firstpreset level and the control means causes the overriding means to movein the first direction, or until the engine speed falls below anotherpreset level that is below the first preset level and the control meanscauses the overriding means to move in the second direction.

Another embodiment of the invention provides overriding means movablewithin a predetermined reference zone adjacent the reference positionand intermediate the open and closed throttle positions thereof, and theoverriding means moves at a relatively slow rate of movement during itsmovement within the predetermined reference zone and at a relativelyfast rate of movement during its movement outside the predeterminedreference zone.

Preferably, the relatively fast and slow rates of movement of saidoverriding means are both constant, and it is preferred that themovement of the overriding means in at least one direction should occurat a predetermined constant rate of movement selected to cause theengine speed, in the normally loaded operation thereof, to vary with themovement with minimal lag therebehind and prevent any significantoscillation of the engine speed about the set speed therefor.

Expressed in other terms, the governor includes means for sensing thespeed of the engine, and throttle overriding means operativelyassociated with the speed sensing means for selectively engaging thethrottle means to automatically move it toward the closed positionthereof at a first relatively fast rate of movement when the speed ofthe engine exceeds a preset level and the throttle means is open beyonda predetermined reference zone intermediate the open and closedpositions of the throttle means, and for controlling the movement of thethrottle means in either a throttle opening or throttle closingdirection to provide a second relatively slow rate of movement thereforwhen the throttle means is within the reference zone and is engaged bythe overriding means.

A further embodiment of the invention provides control means responsiveto the sensed engine speed for causing movement of the overriding meansin at least one direction at a predetermined unchanging average rate ofmovement selected to cause the engine speed, in the normally loadedoperation of the engine, to vary with the movement with minimal lagtherebehind and prevent any significant oscillation of said engine speedabout said set speed, and the control means includes means forgenerating and transmitting power pulses to the motor means foroperating the motor means to cause the aforesaid average rate ofmovement of the overriding means, the power pulses exerting relativelylarger maximum forces to insure positive movement of the overridingmeans against the operational resistance imposed thereon and exerting arelatively smaller average force for causing the aforesaid average rateof movement of the overriding means.

Yet another embodiment of the present invention provides aspeed-limiting governor for use with an engine having means forselective driving connection to and disconnection from a power take-offand a vehicle, both individually and simultaneously, and havingmechanically operated throttle means movable between a fully openedposition and a fully closed position for causing variation of the speedof the engine, the governor including means for sensing the speed of theengine; means for sensing the speed of the vehicle; means for generatinga signal when the power take-off is connected to the engine; meansadapted to be connected to the throttle means for selectively overridingthe mechanical operation thereof, the overriding means being movablebetween an open throttle position and a closed throttle position forselectively limiting the speed of the engine and the vehicle torespective set speeds; and control means selectively responsive to thepower take-off connection signal and the sensed engine speed for causingmovement of the overriding means to limit the speed of the engine to afirst predetermined set speed, the sensed vehicle speed for causingmovement of the overriding means to limit the speed of the engine to alevel that limits the vehicle speed to a predetermined set speed, andthe sensed engine speed for causing movement of the overriding means tolimit the speed of the engine to a second predetermined set speed.

The overriding means is preferably movable to a predetermined referenceposition intermediate the open and closed throttle positions and thecontrol means causes the overriding means to move to the referenceposition in response to the signal being generated by the connection ofthe power take-off to the engine, the reference position being selectedto cause the overriding means to limit opening movement of the throttlemeans beyond a position which causes the engine to operate atapproximately the first set speed when the engine is under no load. Itis preferred that the overriding means be movable to a predeterminedreference position intermediate the open and closed throttle positionsand the control means be responsive to the signal generated byconnecting the power take-off to the engine to cause the overridingmeans to move to the reference position at a relatively fast rate ofmovement and thereafter to move at a relatively slow rate of movementduring its movement within a predetermined reference zone adjacent thereference position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view showing the engine and load speed governorof the present invention connected to a transmission, carburetorlinkage, and accelerator pedal of an engine connected to vehicle wheelsby the transmission;

FIG. 2 is a diagrammatic view showing mechanical details of the governorproper;

FIG. 3 shows the throttle linkage of FIG. 1 in a differentconfiguration;

FIG. 4 shows the switch plate of the present governor as connected tothe electronic control portion thereof;

FIG. 5 shows a schematic circuit diagram of an electronic controlproviding for positioning the throttle-limiting means at a referenceposition;

FIG. 6 shows a schematic circuit diagram of the portion of an alternateelectric circuit providing slow motion of the throttle-limiting means inone direction;

FIG. 7 shows a schematic diagram of a portion of an electronic circuitproviding slow motion of the throttle-limiting means as desired; and

FIG. 8 shows a schematic circuit diagram providing for selectivegoverning of load speed, engine speed, and power take off (PTO) speed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the illustrated embodiment shown schematically in FIG. 1, an internalcombustion engine 20 has connected thereto a transmission 22 for drivinga load 24 such as the drive wheels of a truck. The transmission 22 is ofthe usual construction which allows automatic or manual shifting of thegears therein to provide various ratios of speeds between the engine 20and the load 24. Typically, in a truck, the transmission 22 is shiftedinto "low gear" to start the load 24 moving at very low speeds, as froma standing start, so that the engine 20 can operate at a rotationalspeed of thousands of revolutions per minute, where it operates mostefficiently, while the load 24 is eased into motion by a friction clutchor hydraulic connection (not shown) included in the transmission 22, anda very large torque is applied through the gearing of the transmission22 to the axle 26 of the drive wheels 28 of the load 24, it beingunderstood that the engine 20 and the transmission 22 are attached toand part of the load 24. As the drive wheels 28 pick up speed, andbefore the engine 20 reaches some safe limit to its short termrotational speed, such as 4,400 rpm for example, it is desirable toshift the transmission 22 into a "higher gear" ratio where the wheels 28will turn at a higher rpm relative to the engine 20, and the power ofthe engine 20 will be applied through the transmission 22 to the wheels28 to further accelerate their speed until the engine 20 againapproaches its safe rotational speed. This process of accelerating theengine 20 toward its maximum speed and shifting into a "higher gear"continues until the wheels 28 are driving the load or truck 24 along ata safe and suitable road speed, at which time the transmission will bein its nominal "high gear", the load or truck 24 may be running along at50 miles per hour, and the engine 20 may be revolving at 3,000 rpm.

It is desirable that the road speed of the load 24 should be controlledor governed to some safe speed such as 55 miles per hour and it is alsodesirable that the speed of the engine 20 be governed or controlled toits maximum safe speed for long term operation, such as a speed of 4000rpm, and the engine and load speed governor 30 of the illustratedembodiment of this invention has overriding means for limiting the flowof the energy-supplying means or fuel to the engine to automatically andselectively control both speeds with peculiar advantages to each.

The governor 30 is shown schematically in FIG. 1 connected to the loadside of the transmission 22 by the flexible rotary cable 31, which maybe the typical "speedometer cable", and which transmits rotary motion ata speed proportional to the speed of the wheels 28. A gear 32 connectedto the cable 31 inside the housing 33 drives an output gear 34 which isconnected to a speedometer cable C for driving a speedometer S which maybe located on the dashboard of the truck cab. Governor 30 is connectedto the carburetor throttle plate 35 of the carburetor 36 of the engine20 by a flexible pull cable 38 enclosed within a flexible sheath 40 offixed length attached to and extended from the governor 30, as shown inFIGS. 1 and 2. The connection between throttle plate 35 and cable 38 isby means of the throttle arm 42 mounted on throttle shaft 44 to whichthe throttle plate 35 is affixed, and a stud 46 fixed in the free end 48of the throttle arm 42 intermediately thereof forms a mounting point fora pivotable eye fitting 50 which is permanently attached to the free endof the cable 38.

The extended end of the flexible sheath 40 is attached to a bracket 52mounted to the carburetor 36 for holding the end of the sheath 40 ingeneral alignment with the stud 46 and the eye fitting 50 on theextending end of the cable 38. A first tension spring 54 is stretchedbetween a first pin 56 installed near the extremity of the free end 48of the throttle arm 42 and a second pin 58 fixed in relation to thecarburetor 36 for holding the throttle plate 35 in its normallynominally closed or idle position as shown in FIG. 1 in solid lines. Anaccelerator arm 60 is mounted for free rotation on the throttle shaft 44and is connected to the throttle arm 42 by a second extension spring 62stretched between a third pin 64 and a fourth pin 66, the pins beingrespectively fixed in the free ends of the arms 42 and 60. The spring 62is substantially stronger than the spring 54. A stop 68 on an extendingportion 70 of the accelerator arm 60 is biased against the throttle arm42 by the spring 62 under normal idling conditions for the engine 20.

An accelerator pedal 72 is normally biased to an idle position against apedal stop 74 by a third extension spring 76 of suitable strength and issuitably freely pivoted on a pedal shaft 78 for pedal actuation to afull or wide open throttle position (indicated by the numeral 72')against a floorboard stop 80. The lower end of the pedal 72 is connectedto a fifth pin 82 mounted on the free end of the accelerator arm 60 by alink 84 pivotable at the pedal 72 and the pin 82. The link 84 is ofsuitably adjusted length to place the pedal 72, the accelerator arm 60,and the throttle arm 42 simultaneously in their respective normal oridle positions as shown in solid lines in FIG. 1.

When the governor 30 is in its normal or unactuated condition, the cable38 may be freely pulled out from its sheath 40 by pivoting the throttlearm 42 counter-clockwise against the bias of the spring 54. Bydepressing the pedal 72 against stop 80 to its wide open position, theaccelerator arm 60 will be rotated counterclockwise to its wide openthrottle position as shown in broken lines and indicated by the numeral60' in FIG. 1; and the spring 62 will pull the throttle arm 42 to itswide open throttle position as shown in broken lines and indicated bythe numeral 42'.

When the governor 30 has been actuated as described hereinafter, and theeye fitting 50 at the extending end of the cable 38 has been pulled backtoward its normal or idle position as shown in solid lines, thecounter-clockwise movement of the throttle arm 42 will be limitedaccordingly, and the spring 62 will be stretched as necessary toaccommodate any mismatch between the position of the pedal 72 and theposition of the throttle arm 42. The extreme mismatch, as shown in FIG.3, occurs when the pedal 72 is at the wide open throttle position andthe throttle arm 42 has been limited to its idle position by withdrawalmovement of the cable 38, the spring 62 is at its maximum stretchedcondition, and the cable 38 extending from the governor 30 is therebyfully overriding the call from the accelerator pedal 72 for fullthrottle. Intermediate positions of the pedal 72 and the arm 60 areavailable at the will of the operator, as are intermediate positions ofthe throttle arm 42 as permitted by the limiting action of the cable 38.

The pedal 72 is thereby free to be positioned wherever the operatordesires, and so long as the governor cable 38 is in its fully extended,normal, non-limiting position, the accelerator arm 60 and the throttlearm 42 will be biased together by the spring 62 to move as one, and thethrottle plate 34 will open and close according to the position of thepedal 72. If the cable is retracted to limit the throttle opening, thespring 62 will stretch as necessary upon depression of the pedal 72 sothat the accelerator pedal will have a generally normal feel just as aconventional accelerator pedal and throttle linkage. The acceleratorpedal and throttle and carburetor linkage disclosed is schematic andrepresentative of infinite mechanically equivalent variations to suitparticular engine-carburetor-vehicle combinations. Particularly, torsionsprings may be substituted for the tension springs disclosed, for spaceand configuration considerations, and a similar apparatus could beadapted for use with the control lever of a Diesel or gasoline fuelinjection system, or other means of limiting the flow ofenergy-supplying means to a motor or engine, even an electric one.

The construction and operation of the load speed governor portion 86 ofthe present invention as shown in FIG. 2 is generally the same as thatdisclosed in my aforesaid patent, and no further disclosure is neededherein except to point out the additional elements incorporatedtherewith as shown in FIGS. 2 and 4 to provide means for moving thecarrier 88 to a predetermined reference position upon actuation of theengine speed governor portion 90 of the engine and load speed governor30:

An arcuate switch plate 92 is mounted to pivot for adjustment about thecarrier shaft 94 which is affixed to the housing 33 by means of abracket 96 attached inside the housing. The plate 92 is formed ofinsulating material and is mounted on a metal hub 98 which is mountedfor pivoting on the shaft 94. The hub 98 has an attachment flange 100 towhich the plate 92 is fastened by rivets 102. The plate 92 is locateddirectly behind the carrier 88 within the housing 33, and the bracket 96supports the shaft 94 between the carrier 88 and the hub 98. The shaft94 and hub 98 mounted thereon extend rearwardly through an opening inthe housing 33. Outside the housing 33 a crank arm 104 is attached tothe hub 98 and has an extending end in which is mounted a pivotable stud106 having a threaded cross hole into which is threaded an adjustmentscrew 108. The shank of the screw 108 at the head end thereof passesthrough a clearance hole in a stud 110 fastened to the outside of thehousing 33, and a compression spring 112 mounted on the screw 108between the studs 106 and 110 holds the two studs 106 and 110 biasedfirmly apart to a distance limited by the head 114 of the screw 108.

Thus, rotary adjustment of the screw 108 acts to change the distancebetween the studs 106 and 110, thereby pivoting the switch plate 92about the shaft 94 to set the plate 92 at any desired position within asuitable range of adjustment. Such positioning is desirable in order toangularly place a reference position contact 116 as desired in relationto the carrier 88. The contact 116 is mounted on the switch plate 92 inarcuate relation to the hub 98, and is connected to an electrical lead118 for connection to the electronic control portion 119 of the governor30 as explained hereinafter. The contact 116 extends clockwise from agenerally central portion of the arcuate shape of the plate 92, and asomewhat similar limiting contact 120 is mounted on the plate 92 spaceda small gap 122 counter-clockwise from the contact 116 and extendingalong the same arc as contact 116 in a counter-clockwise directiongenerally to the left side of the plate 92. The contact 120 is connectedto an electrical lead 124 for connection to the electronic controlportion 119.

An electrically conductive spring leaf 126 having a carrier electricalcontact 128 at one end thereof is fastened at the other end to the rearside of the carrier 88 by rivets 130 (see FIG. 2) and is sprung awayfrom the carrier 88 for spring-biased contact with the switch plate 92and the contacts 116 and 120 along the arcs thereof wherever the carrier88 may be positioned as explained in my aforementioned patentapplication or to be explained hereinafter. By its connection to thecarrier 88, the contact 128 is a grounding contact so far as theelectronic control portion of the governor is concerned. In FIG. 4 thecarrier 88 has been broken away, and the spring leaf 126 and the contact128 are shown in more detail in relation to the switch plate 92. Theleft, or counterclockwise end of the reference position contact 116forms the actual reference point or position to which the carriercontact 128 is moved and homed for establishing a reference position forthe carrier 88 and thereby the overriding means for limiting the flow ofenergy-supplying means which is an object of the present invention.

A reversible electric motor 132 is included in the electronic control119, as are the accelerate or open throttle contact 134, the decelerateor close throttle contact 136, and the grounding contacts 138 whichcontrol the motor 132 at the command of the load speed governor 86 toturn the lead screw 140 which in turn causes the carrier 88 to move inrotation on the shaft 94.

In simplest terms, the governor 30 of the present invention functions asfollows: In the absence of a signal to the contrary, either from theload speed governor 86 or the engine speed governor 90, the load speedgovernor 86 acts to move the carrier 88 to its extremecounter-clockwise, rest, or wide-open-throttle position as shown in FIG.2, where the flow of fuel or energy-supplying means to the engine 20 isnot limited at all by the governor 30, but is dependent upon theoperator-positioned accelerator and throttle linkages as describedhereinbefore and in my aforementioned prior patent application. Then, inthe absence of a load speed sufficient to actuate the load speedgovernor 86 as described in my aforesaid patent (e.g. when thetransmission 22 is in neutral, or in a lower gear ratio where the enginemust reach a speed far above the governed speed in order to actuate theload speed governor 86) the electronic control 119 may assume control ofthe governor 30 as explained hereafter.

The electronic control 119 monitors the speed of the engine 20 fordetection of operation of the engine at a predetermined governed or setspeed such as 4000 rpm, and at at least three other speeds havingpredetermined relations to the set speed: A precall speed which may be600 rpm below the set speed, a close throttle speed which may be 400 rpmbelow the set speed, and an overspeed speed which may be 300 rpm abovethe set speed.

Upon acceleration of the engine and detection of the precall speed, 3400rpm in this example, the control 119 initiates a timing circuit, and, ifwithin a predetermined time period such as 0.2 seconds, the closethrottle speed of 3600 rpm or above is detected, then the control 119will connect electrical power (from the engine electrical system) to themotor 132 to cause it to rotate in close throttle direction, therebyturning the lead screw 140 appropriately to cause the carrier 88 to movein clockwise or close throttle direction away from its rest position.Once initiated, this close throttle movement of the carrier 88 willcontinue until the carrier contact 128 touches the reference positioncontact 116, thereby automatically moving the carrier 88 to a referenceposition which has been preset to allow an unloaded engine speed justslightly above the set speed (4000 rpm in this example) of theelectronic control 119. If acceleration of the speed of the engine 20from 3400 rpm to 3600 rpm takes longer than 0.2 seconds, the control 119takes no further action, and the engine speed governor 90 remainsunactuated until the engine speed reaches the 4000 rpm set speed, atwhich time the control 119 energizes the motor 132 in the close throttledirection to move the carrier 88 to its reference position.

If upon arrival of the carrier 88 at its reference position, the enginespeed is detected by the electronic control 119 to be at 4000 rpm orwithin a range thereabove extending to 4300 rpm (the overspeed speed inthis example), then the electronic control 119 will react to the carriercontact 128 touching (thereby making electrical contact with) thereference position contact 116 by reversing the energization of themotor 132 to the open throttle mode, whereupon the carrier 88 is movedcounterclockwise until the carrier contact 128 breaks contact with thereference position contact 116. Once the electrical circuit betweencontacts 128 and 116 is broken, a continuing detection of an enginespeed within the aforesaid range of 4000-4300 rpm causes the control 119to again energize the motor 132 in the closed throttle direction todrive the carrier contact 128 back to the reference position contact 116for continuing repetition of the open throttle-close throttle drivingcycle in a so-called "alternating circuit" mode of operation so long asthe engine speed remains in the 4000-4300 rpm range. In the preferredembodiment of the present invention, the movement of the carrier contactduring the repetitive cycle may be only 0.005-0.010 inch, so that thecable 38 may move little or none, what with normal clearances andbacklash in the apparatus. The throttle plate 35 is thus limited tobeing opened to a corresponding reference position, even though theaccelerator pedal may be fully depressed, and will initially be closedto the reference position by the overriding action of the carrier 88. Ifupon arrival of the carrier contact 128 at the reference contact 116,the engine speed is below 4000 rpm, the control 119 will reverse themotor 132 to the open throttle direction and release control of themotor 132 to the load speed governor contacts 134 and 138 for return ofthe carrier 88 to its wide-open-throttle or rest position.

If upon arrival of the carrier contact 128 at the reference contact 116the engine speed has reached the overspeed speed of 4300 rpm, then thecontrol 119 will cause the electrical contact between contacts 128 and116 to be ignored, and the carrier 88 will continue to be driven inclose throttle direction past the reference contact 116 until thecontrol 119 detects engine speed within the 4000-4300 rpm range or thecarrier reaches its maximum close throttle, idle, or overspeed position.This condition normally will occur only when an overrunning load hasbeen applied to the governed engine, such as running the associatedvehicle down a steep hill, or when the switch plate 92 has beenmiss-set. Upon deceleration of the engine speed to within the 4000-4300rpm range, the control 119 will energize the motor 132 in the openthrottle direction until the carrier contact 128 loses contact with thereference position contact 116 and the governor 90 will revert to thealternating circuit mode of operation.

In normal operation, three operating conditions should be considered,the first being that where the engine cannot maintain the governed orset speed with the throttle plate 35 at its reference position becauseof a heavy load such as an uphill grade, so that engine speed fallsbelow the exemplary 4000 rpm set speed after having attained it underfull throttle and actuated the carrier 88 toward its reference positionto limit the throttle plate 35 to some lesser opening. As soon as theengine reacts to moving the throttle plate toward its reference positionby decelerating below 4000 rpm, the governor 90 will be deactuated bythe control 119, and the carrier 88 will be moved toward open throttleuntil the engine again accelerates to the set speed of 4000 rpm, whichwill reverse the carrier into movement toward closed throttle onceagain--thus the throttle plate 35 will oscillate through a limited rangeof positions as necessary to hold the engine speed very near the setspeed, the frequency and magnitude of the oscillations of the throttleplate 35 and the engine speed being determined by the interrelationshipsof engine power, load applied, and gear ratio being used in thetransmission 22, or accelerational decelerational capacity of theengine, together with the response speed of the motor 132 and its screw140 driving the carrier 88.

The second operating condition is that where the reference position ofthe throttle plate 35 is just sufficient to maintain the engine speed inthe 4000-4300 rpm range--in this case, the control 119 will keep thegovernor 90 in its alternating circuit mode of operation, and the enginespeed may wander within the 4000-4300 rpm range while the throttle plate35 is held at its reference position (assuming that the acceleratorpedal 72 is held depressed at least sufficiently to open the throttleplate 35 that far). If the engine speed goes outside the 4000-4300 rpmrange, the governor 30 will be de-actuated below 4000 rpm or go into theoverspeed mode of close throttle drive as explained hereinbefore above4300 rpm.

The third operating condition is that where an overrunning running loadsuch as a moderate downhill grade is imposed on the engine 20 such thatwhen the governor 30 has acted to close the throttle plate 35 to itsidle or overspeed position, as previously explained, then the enginespeed drops below 4300 rpm, thereby causing the carrier 88 to move backtoward its reference position. Assuming the accelerator pedal 72 beingsufficiently depressed, the throttle plate 35 will open until the enginespeed again goes above 4300 rpm and the control 119 causes the carrierto move in close throttle direction again, and the cycle will repeat,allowing small oscillations of the throttle plate 35 about an averageposition permitting an engine speed of about 4300 rpm and smalloscillations of the engine speed about 4300 rpm. Here again, theparameters of engine accelerational/decelerational ability, gear ratio,and carrier 88 response time determining the period and magnitude of theoscillations.

Operation of the engine 20 at speeds below the set speeds is perfectlyfree of any control by the engine speed governor 90 except in theaforementioned case of rapid acceleration between precall and closethrottle speeds of 3400 and 3600 rpm respectively.

An electronic logic module 144 (not shown in FIGS. 1 and 2) for theelectronic control portion 119 of the governor 90 is mounted within thehousing 33 of the governor 30. As shown schematically in FIG. 5, themodule 144 includes conventional integrated circuits and electroniccomponents which operate as described below to receive negative pulsesignals from an internal conbustion engine ignition coil (oralternatively from a pulse generator connected to a Diesel engine orother prime mover), and signals from the switch plate contact 116 andthe open and close throttle contacts 134 and 136 respectively, in orderto control the reversible electric motor 132 as described hereinbefore.

To control engine speed a method is first needed to detect the enginespeed. This is accomplished by a frequency to voltage converter. Theengine speed is proportional to the number of ignition pulses per minuteas monitored at the negative terminal of the ignition coil of the engine20. These pulses are fed into terminal A. Voltage divider resistors R1and R2 are selected so that the transistor Q1 (normally off) will turnon once for each ignition pulse. A resistor R3, a variable potentiometerP1 and a capacitor C1 form a resistor-capacitor timing network. For eachignition pulse, the transistor Q1 will turn on, and in turn fullydischarge the capacitor C1. As the engine speed increases, thetransistor Q1 will turn on more frequently. With the transistor Q1 off,the capacitor C1 starts to charge. As the voltage rises on the capacitorC1 to approximately 1/2 of the ten volt supply voltage, the logicnorgate IC1-1 of the quad norgate IC1 will have its output (pin 3)change state from high to low. When the output is high, the capacitor C2is being charged through the resistor R4. A change in output from highto low will cause the capacitor C2 to be discharged. By properlyselecting the values of R3, P1, C1, R4 and C2, an average voltage willappear on the capacitor C2 which is proportional to engine speed. Thefaster the engine speed (ignition pulses) the higher the voltage, theslower the engine speed the lower the average voltage.

A voltage comparator circuit is used to determine when variouspredetermined engine speeds occur. The speeds are: precall, closethrottle, governed, and overspeed. The circuit consists of a quadvoltage comparator IC2 and five resistors R19, R5, R9, R10, and R11which set the individual voltages at which each comparator functions.

The precall and close throttle comparators operate cooperatively insequence. Their purpose is to determine whether the engine isaccelerating in speed so fast that the engine speed governor should beactuated before the set speed is reached. If this condition occurs, theprecall and close throttle comparators IC2-1 and IC2-2 act together tostart the governor operating even before the predetermined governedspeed is reached. A typical example would have the precall speed set at3400 RPM, the close throttle speed at 3600 RPM, the governed speed at4000 RPM and the overspeed at 4300 RPM. If the engine should acceleratebetween 3400 and 3600 RPM within 200 milisec, this rate of accelerationwould cause the close throttle norgate IC1-2 to function to operate andactivate the governor. When the engine speed increases at a slower ratethe precall close throttle circuitry is inoperative and plays no part inthe operation.

Upon reaching 4000 RPM, the governor or set speed comparator IC2-3begins its normal governing. At 4300 RPM the overspeed comparator IC2-4turns on, causing the governor 90 to go toward completely closing thethrottle plate 35.

When the engine acceleration exceeds the normal governor reactioncapability, the close throttle comparator IC2-2 causes the control 119to start the governing process prior to 4000 RPM being reached. In theevent of such a condition, the precall and close throttle comparatorsIC2-1 and IC2-2 provide signals to the close throttle norgate IC1-2which in turn provides a signal to a flip-flop circuit composed of thetwo norgates IC1-3 and IC1-4. With the proper signal the flip-flopcircuit is set so that the output of pin 4 of IC1-4 goes high and actsthrough the norgates IC3-1 and IC3-2 of the quad norgate IC3 to causethe transistor Q2 to drive the motor 132 and the associated carriercontact 128 in the close throttle direction. Upon the carrier contact128 reaching the normally open reference position contact 116 of theswitch plate 92 the flip flop circuit receives a reset signal from thenorgate IC3-3 at pin 5 of the norgate IC1-4 and pin 4 thereof goes low.The precall close throttle function cannot reoccur unless the enginespeed drops below the 3400 RPM precall level, and only then could theprocess be repeated.

The quad norgate IC3 comprises the logic circuitry which allows theelectronic logic module 114 to control the governor 90 in propersequence. Pin 6 of norgate IC3-1 is normally low. With a high signal atpin 6, the output pin 4 of norgate IC3-1 goes low and causes the outputpin 10 of norgate IC3-2 to go high. This will turn on the transistor Q2and drive the motor 132 in the close throttle direction. The motorcontinues driving the carrier 88 in the close throttle direction untilits contact 128 reaches the reference position contact 116. Groundingthe reference contact 116 causes pin 2 of the norgate to go low and pin3 thereof to go high. Pin 3 going high will cause pin 10 of the norgateIC3-2 to now go low. When pin 10 goes low, it causes pin 11 of thenorgate IC3-4 to go high which turns on the transistor Q3, driving themotor 132 in the open throttle direction. The carrier 88 going in theopen throttle direction will remove the carrier contact 128 from thereference contact 116 and change pin 2 of the norgate IC3-3 from lowback to high and the process will keep repeating. This operation isknown as the alternating circuit feature since the motor 132 willalternately drive the carrier contact 128 on and off the referencecontact 116. The amount of movement is very small and effectively keepsthe carrier 88 at its reference position at the threshold of thereference position contact 116.

Should the engine speed keep increasing to 4300 RPM as does happen insome isolated instances, it is necessary that the alternating circuitmode be overridden so that the motor will drive the carrier contact 128past the threshold of the reference contact 116 fully in the closethrottle direction. When such an instance is detected by the overspeedcomparator IC2-4, pin 14 thereof goes high and continually holds pin 3of the norgate IC3-3 low. This overcomes the effect of the referencecontact 116 being grounded at pin 2 of the norgate IC3-3 and allows pin10 of the norgate IC3-2 to remain high as long as the overspeedcondition exists. Dropping below the overspeed value of 4300 RPM allowsthe governor comparator IC2-3 circuitry to govern as normal.

The Zener diode Z1 in series with the resistor R 18 across the 12 voltbattery supply voltage, as shown in FIG. 5, provides a stabilized 10volt supply for the logic module 144 as indicated at various pointstherein.

An alternative second embodiment of the engine speed governor 90provides for operation of the motor 132 (and thereby the carrier 88) ata substantially slower speed in open throttle direction than in closethrottle direction--approximately 15-18 seconds to rotate the carrier 88from idle position to wide-open-throttle position as compared to about 3seconds to rotate it from wide-open-throttle to idle position. Theslower speed is accomplished by the circuitry of FIG. 6, which shows inschematic detail the changes and additions to the circuitry of FIG.5--the portions of FIG. 5 which are not repeated in FIG. 6 are identicalin both circuits. The additional resistor R20 in the connection betweenthe transistor Q3 and the motor 132 serves to reduce the voltagesupplied to the motor, and with the resultant reduced speed, it isdesirable that, upon arrival of the carrier contact 128 at the referencecontact 116 subsequent to actuation of the governor 90, that the contact128 should remain at the reference contact so long as the engine speedremains in the 4000-4300 RPM range. Therefore, the pin 13 of the norgateIC3-4 is now connected to limiting circuitry comprising the transistorsQ4, Q5, and Q6 and their associated added components. Now, when thecontact 128 touches the contact 116, the motor 132 is turned off, and solong as the engine speed remains in the 4000-4300 RPM range, it remainsoff. If the engine speed drops below 4000 RPM, the governor comparatorIC2-3 will cause the motor 132 to run in open throttle direction (at theslow speed) until the engine again rises to 4000 RPM, or until thecarrier 88 moves in open throttle direction sufficiently for the carriercontact 128 to cross the narrow gap 122 and touch the limiting contact120 on the switch plate 92--in either case, the open throttle driveceases; and in the first case the governor comparator IC2-3 causes themotor 132 to drive in the close throttle direction, while in the secondcase the carrier contact 128 remains at the limiting contact until theengine either rises to 4000 RPM and the governor comparator IC2-3 causesclose throttle drive, or the engine drops below the precall speed of3400 RPM and the precall comparator IC2-1 causes open throttle drive,carrying the carrier contact 128 past its initial contact with thelimiting contact 120 toward the wide-open-throttle position of thecarrier 88.

This second, slow speed, embodiment is advantageous for lessening enginespeed oscillations, but is disadvantageous in that the slow travel ofthe carrier 88 toward open throttle may sometimes handicap the operatorwho is trying to get a rapid acceleration of the engine for shiftinggears.

Yet a third embodiment of my engine speed governor invention providesfor normally fast travel of the carrier 88 toward its reference positionupon actuation of the engine speed governor 90 until the carrier contact128 moves off the limiting contact 120, at which the motor 132 drops toa very slow speed resulting in clockwise movement of the carrier 88about its shaft 94 at the rate of about one-third RPM, which would beroughly equivalent to full travel from wide-open-throttle position toidle throttle position in about thirty seconds. An objective of thisslow speed is to move the carrier 88 in limiting control of the throttleplate 35 at a slower rate than the response capability of the engine 20,thereby minimizing engine speed oscillations. Since the responsecapability of the engine will vary considerably according to loads andgear ratios, recovery time (from the loss of engine speed due to suddenapplication of a heavy load while running at the governed speed underlight load) could be somewhat slow--however, this is not the usualcondition and is overweighed by the stability of the system for normaloperation.

The relation of engine response capability rate and throttle limitingmeans movement rate is a complex one, but consider that any enginerunning at idle speed and having full throttle suddenly applied willtake a second or two to reach a speed of say 4000 RPM, and if a governoracts to close the throttle quickly to closed or idle throttle positionupon attainment of the 4000 RPM speed, the engine speed will overshootor overrun the 4000 RPM speed and then decelerate below the 4000 RPMspeed and undershoot or underrun it, even though the governor acts toopen to full throttle again immediately upon the speed dropping below4000 RPM. This may cause oscillations of engine speed of 1000 RPM ormore in an unloaded engine, rapidly enough to be disturbing to itsoperator, and resulting in a governor with very poor regulation. This isan example of a throttle limiting means moving at a very much fasterrate than the engine response capability rate, and results inout-of-phase operation of engine and throttle as explained in myaforesaid prior patent.

On the other hand, it has been found that where the throttle can only bemoved between idle and full positions over a period of about twentyseconds or more, then in-phase operation of engine and throttle occurs,as in the present invention, and very good governor regulation can beobtained. The engine has the capability of increasing its speed withvery little lag behind the throttle position, even under heavy or fullload, meaning that if the throttle is opened half-way at this slow rateor slower, that the engine will have come up in speed slowly with theslow opening and will have achieved its maximum sustained speed for thisthrottle opening and particular load momentarily after the throttlemovement stops, and will overrun the aforesaid maximum sustained speedinsignificantly, thereby staying essentially in phase with the throttle,even under no load conditions. In the commercial engine applicationrange considered so far, an approximately twenty to twenty-five secondthrottle movement period seems about the optimum for satisfactorygovernor regulation for a smoothly operating governor and a period asshort as seven or eight seconds causes objectionable oscillations. Ofcourse, to obtain satisfactory restraint under no load engine run-upconditions and satisfactory recovery from sudden load applications, itis desirable to have fast throttle closing upon sudden acceleration ofthe engine, and fast throttle opening upon sudden deceleration. Theapparatus of the present invention provides such capability for bothfast and slow throttle movement through the use of a reference positionfor the throttle limiting means, such that throttle movement will beslow under normal conditions, but may be swift when needed for recoveryof control of a rapidly fluctuating engine speed caused by some factorexternal to the governor. To date, the apparatus of the presentinvention is the only known solution to this problem for everydaycommercial use, e.g., as for truck and bus engines. Upon arrival at itsreference position, assuming that the engine speed still lies in the4000-4300 RPM range, the carrier stops and remains in place, movingtherefrom only upon detection of engine speed outside the 4000-4300 RPMrange and only at the above-mentioned slow speed, whether in openthrottle or close throttle direction.

When the engine speed drops below 4000 RPM, the motor 132 is energizedat the slow speed in open throttle direction and continues in thatdirection until the carrier contact 128 hits the limiting contact 120and halts there, unless in the meantime the engine speed has risen againto 4000 RPM to cause the motor 132 to be reversed to close throttledirection, or has dropped below the 3400 RPM precall speed which willcause the carrier 88 to continue in open throttle direction, but at highspeed after touching the contact 120. If the carrier contact 128 ishalted upon touching the limiting contact 120, it remains there pendingdetection of engine speed rising to 4000 RPM to cause close throttledrive at the slow speed, or engine speed falling below the 3400 RPMprecall speed to cause open throttle drive just as in the secondembodiment; however, the motor 132 will return to its normal fast speedbecause the carrier contact 128 is contacting the limiting contact 120.

As a practical matter, on a long steep grade in a truck engineapplication, where a considerably open throttle position is required tomaintain the engine at the 4000 RPM governed speed, after the throttlelimiting means has been moved to the reference position, then thegovernor will allow the throttle to slowly open further to a point whereits average position furnishes just the fuel needed to maintain 4000 RPMwith only minor oscillations thereabout as the throttle is opened andclosed slightly by governor detection of engine speed falling below 4000RPM and then rising back to that speed.

The circuitry for obtaining the slow-motor speed in both directions, andonly when the carrier contact 128 is out of contact with the limitingcontact 120, comprises essentially a suitable resistor R31 placed in the12 volt common supply connection to the motor 132 as shown in FIG. 7 inpartial schematic detail. The resistor R31 reduces the voltage acrossthe motor 132 sufficiently to cause it to run at the desirable low speedin close throttle direction where the force of the load speed governorspring 142 and throttle apparatus springs must be overcome, and a secondresistor R30 in the open throttle connection between the transistor Q3and the motor 132 reduces the voltage across the motor even further tocompensate for the overrunning force applied by the governor spring 142and throttle apparatus springs when the motor runs in throttle openingdirection. A PNP transistor Q7 is connected in parallel with theresistor R31 and is controlled indirectly through additional circuitry(not shown) associated with the limiting contact 120 by the conditionthereof. When contact 120 is grounded by contact with the carriercontact 128, the transistor Q7 is caused to be conductive, the resistorR31 is shunted out of the circuit and is of no effect, and the motor 132runs at normal fast speed. When the carrier contact 128 leaves thelimiting contact 120, leaving it ungrounded, then the transistor Q7 goesnon-conducting and all current to the motor 132 must pass through theresistor 31, so that the motor runs at the desirable slow speed.

This third, slow speed, embodiment lessens the oscillations of enginespeed, and would be preferable to the first, alternating circuit,embodiment except that the low motor voltages required to obtain asuitably slow operation of the motor 132 may not provide sufficientstarting torque for reliable motor operation under extreme cold weatherconditions. However, governors 30 according to this third embodimenthave worked satisfactorily in moderate temperature conditions andcommercially demonstrate the advantages of slow speed operation of themotor 132.

A fourth embodiment of my engine speed governor invention provides animproved means for obtaining the aforesaid very slow speed of the motor132 as in the third embodiment disclosed herein, and also provides thatsuch very slow speed operation occurs only when the engine 20 isconnected to a power take-off (PTO) and the engine is automaticallyselectively governed in a PTO mode to a predetermined set speed, such as2000 RPM, e.g., which is safe for operation of the PTO and which may bedifferent from the predetermined set speed for the engine governing modeof operation, which may be 4000 RPM as explained hereinbefore. When thePTO is disconnected from the engine, the engine is automaticallyselectively governed in the engine governing mode by additional meansprovided therefor for operation generally similar to the enginegoverning mode of my aforesaid U.S. patent, but differing particularlyin that the carrier 88 moves initially upon actuation of the enginegoverning mode toward a reference position for the PTO governing modeand normally moves between that reference position and its full throttleposition to govern the engine with considerable oscillation about theengine governing mode set speed, generally as with the apparatus of myaforesaid U.S. patent. In the event that the engine reaches apredetermined overspeed condition above the engine governing mode setspeed and remains at such overspeed for a predetermined time, thecarrier 88 (which serves as a throttle overriding means) will move inclose throttle direction beyond the reference position toward the closedor idle throttle position.

The circuitry for providing the three modes of operation of this fourthembodiment, namely, road or load speed governor or governing, enginespeed governing and PTO speed governing, is adapted for either sparkignited engines or diesel engines, and is shown in FIG. 8. Themechanical apparatus, arrangement, and operation may be the same asshown in FIGS. 1-4 and explained in connection with the otherembodiments disclosed herein.

In general, the circuit comprises a speed signal generator 148 whichdevelops an analog speed voltage corresponding to the value of enginespeed. The output of the speed signal generator is coupled with anengine speed comparator 150 which develops a logic signal for use incontrolling the throttle overriding means positioning motor 132. Thelogic signal from the comparator 150 is applied to a logic circuit 152which controls the energization of the motor 132. The output of thelogic circuit 152 is applied to the motor energizing circuit 154. Theclose throttle switching circuit 156 supplies an input signal to thelogic circuit 152 according to the position of the carrier 88 and itscontact 128. Similarly, an open throttle switching circuit 158 suppliesan input signal to the logic circuit 152 according to the position ofthe contact 128. A power supply circuit 160 receives the vehicle batteryvoltage and supplies a regulated output voltage for the integratedcircuits. The system thus far described is operative from the enginespeed governing mode. The system also includes additional stages whichare operative in the PTO governing mode. These additional stages includea PTO mode selector which comprises a PTO selector switch 162, a PTOengaging element 163 for connecting the PTO to the engine 20 andsimultaneously actuating the switch 162, and a flip-flop 164. Theflip-flop 164 supplies an input signal to the logic circuit 152 toinitiate the PTO mode of operation. An oscillator circuit 166 is turnedon by the selector switch 162 and provides an output to the logiccircuit 152 to modulate the energization of the motor 132 in the PTOmode so that the motor 132 is operated at a reduced speed. When the PTOswitch 162 is opened to initiate the PTO mode the flip-flop 164 is setso that the signal supplied to the logic circuit 152 causes the motor132 to be driven in the close throttle direction. The output of theflip-flop 164 is also applied to the oscillator circuit 166 to disablethe oscillator 166 and allow fast movement of the motor 132 to positionthe carrier contact 128 at its close throttle reference position asshown in FIG. 4 in solid lines. When the close throttle referenceposition is reached the close throttle switching circuit 156 drives areset signal to the flip-flop 164 which changes state. When in the resetstate, the flip-flop 164 does not disable the oscillator 166 and doesnot cause the motor 132 to be energized.

The overspeed circuit 168 is used in the engine speed governing mode andthe PTO mode. The overspeed circuit 168 receives the speed signal fromthe engine speed signal generator 148 and produces an output signal tothe logic circuit 152. When the speed is excessive (and remainsexcessive for a predetermined time of a few seconds) the overspeedsignal is effective to override the close throttle switching circuit 156and allows the motor 132 to drive the carrier 88 beyond the closethrottle reference position.

The throttle switching circuit stages will be described later in greaterdetail.

The speed signal generator 148 develops an analog voltage which isproportional to engine speed. For this purpose, the generator 148 isadapted to receive engine ignition coil impulses on coil input 170 fromthe primary winding of the ignition coil of a spark ignited engine. Itis also adapted to receive transducer impulses on transducer input 172from a transducer on a diesel engine. The speed signal generator 148 iscomprised of a frequency-to-voltage converter circuit. The convertercircuit includes an input transistor 174 which is coupled to amonostable multivibrator or one shot 176. The one shot 176 comprises anintegrated circuit and adds an external dividing circuit including thevariable resistors 178 and 180 and the fixed resistor 182 in series witha timing capacitor 184 from ground to the 10 volt supply voltage.Variable resistors 178 and 180 may be adjusted to set the voltage acrossthe capacitor 184 and thereby the governed speed at a desired value forboth the engine governor mode and the PTO governor mode. A switchingtransistor 186 has its output connected in parallel with the variableresistor 178 and its input connected to the PTO selector switch 162.When the selector switch 162 is in the closed position to select thegovernor mode, the transistor 186 is turned on and the resistor 178 isbypassed to set the speed for the engine governor mode. When theselector switch 162 is open, the transistor 186 is turned off andresistor 48 remains in the timing circuit and sets a lower voltageacross the capacitor 184 and thereby a lower speed for the PTO mode.

Assume that the control circuit is applied to an ignition engine and theignition pulses are applied to the coil input 170. (The operation of thecircuit will be the same for a diesel engine with transducer pulsesapplied to the transducer input 172). The input pulses on the input 170are applied through the input circuit to the base of the transistor 174and each pulse turns on the transistor 174. The output of the transistor174 is applied to the input terminal 188 of the one shot circuit 176,and each pulse triggers the one shot circuit 176. Each time the circuit176 is triggered, the output terminal 190 of the one shot circuit 176will be high for a cetain length of time depending upon the timeconstant of the timing circuit. The output 190 is connected across theresistor 192 and the capacitor 194 which is charged to a voltage valuecorresponding to the engine speed. The speed voltage from the terminal196 of the capacitor 194 is applied through the signal input of thecomparator 150 which will be described below.

The speed comparator 150 is adapted to develop a speed logic signal inresponse to the analog speed signal. For this purpose, the speed signalvoltage from the terminal 196 is applied to the noninverting input(which constitutes the signal input) of the comparator 150. A referencevoltage which represents the desired governed speed is applied to theinverting input (the reference input) of the comparator 150. Thereference voltage is derived from the power supply 160. In particular,the battery voltage, plus 12 v, is applied across the series resistor198 and a zener diode 200 to obtain a regulated 10 V voltage for usewith the integrated circuits. The regulated voltage is applied across avoltage divider string of resistors 202, 204 and 206. A referencevoltage for the comparator 150 is taken from the junction of resistors204 and 206 and applied to the reference input of the comparator 150.When the speed voltage on the signal input of the comparator 150 is lessthan the reference voltage, the output of the comparator 150 is at logiclow and when the speed signal voltage is higher than the referencevoltage the output of the comparator 150 is at logic high. This speedlogic signal at the output of the comparator 150 is applied to the inputof the logic circuit 152. It is desirable to have the speed comparator150 switch between high and low outputs in response to somewhatdifferent speed voltages so that there is a range or band of speedvariations around the desired governed value which will not causeswitching of the comparator 150. For this purpose, the comparator 150 isprovided with a hysteresis band in a manner which will be described inconnection with the logic circuit 152.

The logic circuit 152 comprises a NOR GATE 208 which receives the speedlogic signal on a first input and receives a logic signal from theflip-flop 164 on a second input. For purposes of the presentdescription, it will be assumed that the output of the flip-flop 164 isat logic low (which is the case during operation in the engine governormode). The logic circuit also comprises an inverter 210 and a pair ofNOR GATES 212 and 214. The output of the NOR GATE 208 is applied to afirst input of the NOR GATE 214 and it is also applied through theinverter 210 to a first input of the NOR GATE 212. The NOR GATE 214 isadapted to control the energization of the motor 132 in the closethrottle direction through the motor energizing circuit 154. The NORGATE 214 receives a signal from the close throttle switching circuit 156on a second input. It also receives an input from the oscillator 166 ona third input. The output of the NOR GATE 214 is applied to a firstinput of the motor energizing circuit 154 which will be described below.The NOR GATE 212 is adapted to control the energization of the motor 132in the open throttle direction. The NOR GATE 212 receives a signal fromthe open throttle switching circuit 158 on a second input. The NOR GATE212 also receives the output of the oscillator 166 on a third input. Theoutput of the NOR GATE 212 is connected to a second input of the motorenergizing circuit 154 which will be described below.

In order to provide hysteresis switching for the comparator 150, theoutput of the NOR GATE 208 is connected back to the set voltage input ofthe one-shot 176 from the capacitor 184. This feedback loop includes adiode 216 and a resistor 218. When the output of the NOR GATE 208 goesto logic low, current is bled from the capacitor 184, thereby changingthe set voltage and the output of the one shot 176 and the speed voltagefrom the terminal 196.

The motor energizing circuit 154 comprises a power transistor Q3 whichhas its input at the base electrode connected with the output of the NORGATE 214. The output of the transistor Q3 is connected with the closethrottle winding terminal CTW of the motor 132 for energizing the motorin the close throttle direction. The energizing circuit 154 alsoincludes a power transistor Q2 which has its input at the base electrodeconnected with the output of the NOR GATE 212. The output of thetransistor Q2 is connected with the open throttle winding terminal OTWof the motor 132 and to ground through the switch contacts 136 and 134unless they are opened by action of the load speed governor 86 aspreviously described and further described hereinafter.

The close throttle switching circuit 156 comprises a normally openswitch contact 116 connected with the input of an inverter 220. Theswitch contact 116 is grounded by the carrier contact 128 when the motor132 drives the overriding means or carrier 88 to the close throttlereference position as shown in FIG. 4. When the contacts 116 and 128 areclosed the input of the inverter 220 is connected to ground to produce alogic low at the input and a logic high at the output of the inverter220. The output of the inverter 220 is applied to the second input ofthe NOR GATE 214. Accordingly, the switch contacts 116 and 128 are openbefore the motor 132 drives the carrier 88 to the close throttlereference position and the output of the inverter 220 is at logic low.This has no switching effect on the NOR GATE 214. However, when theswitch contacts 116 and 128 are closed the output of the inverter 220 isat logic high and the output of the NOR GATE 214 goes to logic low. Thisturns off the transistor Q3 and deenergizes the close throttle windingterminal CTW of the motor 132.

The open throttle switching circuit 158 comprises a switch contact 120which is normally open and which is closed and grounded by the carriercontact 128 when the motor 132 drives the carrier 88 and the contact 128to an open throttle reference position thereat. The switch contact 120is thereby connected between ground and one input of a comparator 224which is connected to function as an inverting circuit. For this purposethe other input of the comparator 224 is connected with a referencevoltage taken from the junction of resistors 204 and 206 in the powersupply 160. The output of the comparator 224 is connected with thesecond input of the NOR GATE 212. Accordingly, when the contact 120 isopen, the output of the comparator 224 is at logic low and it has noeffect on the NOR GATE 212. When the contact 120 is closed the output ofthe comparator 224 is at logic high and the output of the NOR GATE 212is at logic low. This turns off the transistor Q2 and deenergizes theopen throttle winding terminal OTW of the motor 132.

The overspeed circuit 128 comprises a comparator 226 and a comparator228 which are adapted to respond to an engine overspeed condition andcause the motor 132 to be energized in the close throttle direction todrive the carrier 88 beyond the close throttle reference position in theclose throttle direction. The comparator 226 has a signal input(non-inverting) connected with the terminal 196 to receive the speedsignal voltage. The reference input (inverting input) for thecomparators 226 and 228 is connected to a reference voltage at thejunction of resistors 202 and 204 in the power supply 160. Note that theoverspeed reference voltage is at a higher level than the governed speedreference voltage. The output of the comparator 226 is connected withthe signal input (inverting input) of the comparator 228. The output ofcomparator 226 is also connected to the regulated voltage source througha resistor 230 and to ground through a capacitor 232. The referenceinput (non-inverting input) of the comparator 228 is connected with thereference voltage at the junction of resistors 202 and 204. Accordingly,when the speed voltage at the signal input of comparator 226 exceeds thereference voltage, the output of the comparator 226 goes to logic highand the capacitor 232 starts to charge through resistor 230. When thevoltage across the capacitor 232 exceeds the reference voltage on thereference input of comparator 228, the output of the comparator 228 goesto logic low. The charging time for the capacitor 232 to exceed thereference voltage is approximately five seconds. The output of thecomparator 228 is connected to the second input of the NOR GATE 214.When the output of the comparator 228 is at logic low, it overrides theeffects of the logic signal applied from the contact 116 throughinverter 220 to the same second input. This allows the motor 132 todrive the carrier 88 to a closed throttle position beyond the closethrottle reference position as shown in FIG. 4.

The oscillator circuit 166 is adapted to produce a squarewave outputwith adjustable duty cycle for modulating the energization of the motor132 when the control circuit is operated in the PTO mode. For thispurpose, the output of the oscillator 166, as will be described, isconnected to respective inputs of the NOR GATES 212 and 214. Theoscillator 166 is turned off by the PTO selector switch 162 when it isin the closed position and it is turned on with the switch 162 in theopen position. The oscillator circuit 166 comprises an inverter 234 anda NOR GATE 236. The input of the inverter 234 is connected through thediode 238 to the PTO selector switch 162. The output of the inverter 234is connected through a conductor 240 to a first input of the NOR GATE236. The output of the NOR GATE 236 is connected through a capacitor 242to the input of the inverter 234. A circuit extends from the output ofthe NOR GATE 208 in logic circuit 152 through a resistor 244, diode 246,and diode 248 to the output of the inverter 234. The junction betweenthe diodes 246 and 248 is connected through a resistor 250 and aparallel connected diode 252 to the input of the inverter 234. The NORGATE 236 has a second input which is connected with the output of thecomparator 226 in the overspeed circuit 168. When the output of thecomparator 226 is high, the NOR GATE 236 is inhibited to stop theoscillator 166. A third input of the NOR GATE 236 is connected with theoutput of the flip-flop circuit 164 so that the output of the NOR GATE236 is inhibited and the oscillator 166 is stopped when the flip-flop164 is set, as will be described further below. When the PTO selectorswitch 162 is in the open position to select the PTO mode of operation,the oscillator 166 is operative to produce a train of output pulses onthe output of the NOR GATE 236. This output is applied through aconductor 254 to a third input of the NOR GATE 214 and a third input ofthe NOR GATE 212. This has the effect of modulating the drive current tothe motor 132 i.e. it reduces the average value of the input current tothe motor 132 and causes the motor to operate at reduced speed yet withhigh torque during the pulses for reliability of operation at very slowspeeds as compared to the slow speed at low constant direct currentvoltage as in the third embodiment of the present invention.

The flip-flop circuit 164 is adapted to initiate the operation of thecontrol circuit in the PTO mode in response to opening of the PTOselector switch 162. The flip-flop circuit 164 comprises a pair ofcross-coupled NOR GATES 256 and 258. The PTO selector switch 162 isconnected between ground and a first input of the NOR GATE 258 through acapacitor 260. The first input is connected to ground through a resistor262. The second input of the NOR GATE 258 is coupled with the output ofNOR GATE 256. The output of the NOR GATE 258 is coupled with a firstinput of the NOR GATE 256 and the second or reset input of the NOR GATE256 is connected with the output of the inverter 220 in the closethrottle switching circuit 156. The output of the NOR GATE 256 isconnected across a capacitor 264 and to the second input of the NOR GATE208 in the logic circuit 152. The output of the NOR GATE 256 is alsoconnected to the third input of the NOR GATE 236 in the oscillator 166.When the PTO selector switch 162 is opened, the first input of the NORGATE 258 goes to logic high and the output thereof goes to logic low.This causes the output of the NOR GATE 256 to go to logic high. The highoutput from the NOR GATE 256 is applied to the third input of the NORGATE 236 and disables the oscillator 166. This allows the motor 132 todrive the carrier contact 128 at full speed to its close throttlereference position as shown in solid lines in FIG. 4. The high output ofthe NOR GATE 256 on the second input of the NOR GATE 208 causes theoutput of the NOR GATE 208 to go to logic low. This causes the output ofthe NOR GATE 214 to go to logic high and the transistor Q3 is turned onto energize the motor 132 in the close throttle direction. When themotor 132 drives the contact 128 to its close throttle referenceposition, the contact 116 is grounded and the output of the inverter 220goes to logic high. The output of the inverter 220 is applied to thereset input of the NOR GATE 256 and the flip-flop 164 is reset with theoutput of the NOR GATE 256 at logic low. This causes the transistor Q3to turn off and it also allows the oscillator 166 to operate.

When the PTO selector switch 162 is in the closed position, the systemoperates in the engine governor mode. In this mode, a speed signalvoltage is developed by the signal voltage generator 148 across thecapacitor 194. This speed signal voltage is applied to the signal inputof the comparator 150. The governed speed is established by thereference voltage across resistor 206 which is applied to the referenceinput of the comparator 150. When the engine speed is below the governedspeed, the output of the comparator 150 is at logic low. This causes theoutput of the NOR GATE 208 to be at logic high and the output of NORGATE 212 to be at logic high. This causes the transistor Q2 to turn onand the motor 132 is energized in the open throttle direction. When themotor 132 drives the contact 128 into contact with the contact 120 (theopen throttle reference position), the contact 120 is grounded and theoutput of the comparator 224 (operating as an inverter) goes to logichigh, but the output of the comparator 224 is grounded through the diode266 and the switch 162 so that the NOR GATE 212 is not affected and themotor 132 continues to drive in the open throttle direction so long asthe engine speed remains below the governed speed.

When the engine speed signal voltage is larger than the referencevoltage, the output of the comparator 150 is at logic high. This causesthe output of NOR GATE 208 to go to logic low and the output of the NORGATE 214 to go to logic high. This turns on the transistor Q3 whichenergizes the motor 132 in the close throttle direction. When the motor132 drives the contact 128 to the close throttle reference position thecontact 116 is grounded and the output of the inverter 220 goes to logichigh. This causes the output of the NOR GATE 214 to go to logic low andthe transistor Q3 is turned off and the motor 132 is deenergized.

In this engine governor mode of operation, the engine speed ismaintained around the governed speed, but with considerable oscillation,by the operation of the motor 132 driving the contact 128 back and forthwithin the limits of its close throttle reference position and itswide-open throttle position (which is beyond its open throttle referenceposition). In the event that the engine reaches an overspeed condition,the output of the overspeed circuit 168 goes to logic low and overridesthe effect of the grounding of the contact 116 by the contact 128 at itsclose throttle reference position. This causes the output of the NORGATE 214 to go to logic high which keeps the transistor Q3 turned on todrive the motor 132 to drive the contact 128 beyond its close throttlereference position.

When the PTO selector switch 162 is opened, the operation of the controlcircuit in the PTO mode is initiated. The opening of the switch 162 iseffective to set the flip-flop 164 so that the output of NOR GATE 256thereof goes to logic high. This causes the output of NOR GATE 208 to goto logic low and the output of NOR GATE 214 to go to logic high turningon the transistor Q3 and energizing the motor 132 in the close throttledirection. At the same time, closure of the switch 162 turns on theswitching transistor 186 in the speed signal voltage generator 148 andbypasses the resistor 178. This changes the output of the signalgenerator 148 to a value corresponding to the PTO governing mode. Also,the output of the flip-flop circuit 164 in the set condition disablesthe oscillator circuit 166. When the motor 132 drives the contact 128 toits close throttle reference position, the contact 116 is grounded andthe output of the inverter 220 resets the flip-flop 164. Thus thetransistor Q3 is turned off and the motor 132 is deenergized and theoscillator 166 is enabled.

In the PTO governing mode the circuit operates to maintain the enginespeed at the PTO governing value in the manner as described for theengine governing mode except that the motor energization is modulated bythe oscillator circuit 166 and the motor is operated only to move thecontact 128 in a reference zone lying between its open throttlereference position and its close throttle reference position after itsinitial movement to its close throttle reference position upon openingof the PTO switch 162, the gap 122 between the contacts 116 and 120being suitably large to allow sufficient opening of the throttle 35 tomaintain governed speed under normal PTO loading. This mode of operationprovides a relatively very slow movement of the carrier 88 and itscontact 128 when the oscillator 166 is enabled, yet the pulses of themodulated current assure that the motor 132 exerts sufficient torque toreliably overcome the operational resistance of the governing elementswhich the motor 132 drives.

Control of the motor 132 by the load speed governor 86 (through movementof the carrier 88 and its open throttle and close throttle contacts 134and 136 respectively, by action of the flyball mechanism 142 to move thegrounding contacts 138) is the same as that disclosed in myaforementioned prior patent, whereby the load speed governor canoverridingly run the motor 132 in close throttle direction in responseto suitably high load speed at any time, and the engine speed governor90 can do likewise at any time in response to a suitably high enginespeed whether operating in engine governing or PTO governing mode, butthe load speed governor can only run the motor 132 in open throttledirection in response to a suitably low load speed when the engine speedgovernor 90 is also calling concurrently for the motor to operate inthat direction in response to a suitably low engine speed by making thetransistor Q3 conductive, and vice-versa.

The fourth embodiment of the present invention offers two mainadvantages over the other three embodiments disclosed herein:

First, provision of a PTO governor in combination with an engine speedgovernor and a road speed governor means that a separate operator is notrequired to control the engine of a vehicle while a power take-off isbeing used, such manual control being difficult, demanding, and chancyin that complete attention is required to loading which may changefrequently and unexpectedly. Also, the PTO-driven equipment may bedamaged by inadvertent operation above relatively slow safe speeds, suchas 1200 RPM or 2000 RPM, and PTO's are often inadvertently left engagedwhile the vehicle to which attached is put into over-the-road operationand the engine is operated at high speeds capable of damaging thePTO-driven equipment. This fourth embodiment eliminates all possibilityof overspeeding damage to the engine or PTO-driven equipment and ofunsafe vehicle speeds, for the present governor will automaticallyselectively govern the engine to limit it to a suitable predeterminedset speed for engine, PTO, or vehicle, as needed, while not otherwiserestricting their operation.

Second, provision of a modulating circuit for powering the governordrive motor 132 permits selective operation of the motor 132 at normalhigh speed, normal torque, and normal voltage, as well as at arelatively very low speed but still with normal torque and normalvoltage, thereby assuring reliable operation at the low speed. Providingtwo such speeds mechanically, as by change gears, or conventionallyelectrically, as in the third embodiment disclosed herein, appeardisadvantageous.

Operation of this fourth embodiment of my invention in the load or roadspeed governing mode is the same as that in the other embodiments.Operation in the engine governing mode is generally like that in myaforementioned patent except that the carrier 88 is normally limited tomovement between its wide open throttle position and its closed throttlereference position for PTO governing mode as determined by the settingof the adjustable arcuate switch plate 92 and exemplified by thesolid-line position of the contact 128 in FIG. 4. This additionallimitation on the movement of the carrier 88 seems to be of little, ifany, practical effect, since the closed throttle reference position forPTO mode allows only a small throttle opening beyond the full closed oridle throttle position.

Operation in the PTO governing mode of this fourth embodiment differsfrom operation in the engine governing mode of the third embodimentdisclosed hereinbefore (which it most resembles) in various aspects asexplained hereinafter. No precall for the carrier 88 to the closethrottle reference position is based on engine speed in this fourthembodiment. Rather, the PTO engaging element 163 is commonly manuallyactuated while the throttle 35 is in idle position as in FIG. 3, therebyactuating the PTO selector switch 162 and causing the carrier 88 to moveto its predetermined close throttle reference position at a relativelyhigh rate of movement as explained hereinbefore. The carrier 88 stops atthat position, and then the throttle operating mechanism is commonlymanually moved to, and locked at a relatively wide open position whilethe overriding carrier 88 limits the throttle 35 from opening beyond aposition which causes the engine 20 to operate under no load atapproximately the desired predetermined set PTO governing speed, e.g.2000 RPM.

Upon application of a load to the PTO-driven equipment, the speed of theengine 20 will immediately fall below the PTO set speed and the motor132 will be energized as described hereinbefore by pulses of electricalcurrent or power to cause movement of the carrier 88 and the throttle 35in throttle opening direction at a predetermined unchanging average rateof movement selected to cause the engine speed to vary with the movementwith minimal lag therebehind to prevent any significant PTO or enginespeed oscillation about the predetermined set PTO speed. The current orpower pulses may be of generally equal maximum amplitude as the currentsupplied for unmodulated energization of the motor 132, and exertrelatively larger maximum forces than their relatively smaller averageforce to insure positive movement of the carrier 88 against theoperational resistance imposed thereon and at the same time to cause theaforesaid average rate of movement thereof, which is relatively slow.

The present invention has been described in detail above for purposes ofillustration only and is not intended to be limited by this descriptionor otherwise to exclude any variation or equivalent arrangement thatwould be apparent from, or reasonably suggested by, the foregoingdisclosure to the skill of the art, such as the substitution of vacuumor mechanical or other actuators, for the electrically driven lead screwdisclosed herein, the substitution of centrifugal or magnetic or otherengine speed responsive means for the electronic module disclosedherein, or the substitution of magnetic or electronic or other loadspeed responsive means for the fly ball mechanism disclosed herein.I.e., the scope of the present invention is to be determined by thescope of the appended claims.

I claim:
 1. In an engine speed governor for an engine having a throttlemovable between an open throttle position and a close throttle positionfor regulating the flow of fuel to the engine, said governor being ofthe type comprising an overriding throttle closing means, engine speedsensing means for producing a speed signal, and control means for movingthe throttle closing means to a position for limiting the engine speedto a predetermined governed value, the improvement wherein said controlmeans included:actuating means including a reversible motor coupled withthe overriding throttle closing means for driving it in the closethrottle direction or the open throttle direction, electronic circuitmeans coupled with said speed sensing means and with said motor forenergizing the motor, said circuit means including means responsive to apredetermined speed signal for energizing the motor for relatively highspeed operation in the close throttle direction until the overridingthrottle closing means reaches a reference position, said circuit meansincluding means for energizing the motor for relatively low speedoperation in either the close throttle or open throttle direction afterthe overriding throttle closing means reaches said reference position,said low speed operation of the motor being slower than the responsecapability of the engine to a change in flow of fuel to the enginewhereby engine speed oscillations are minimized.
 2. The invention asdefined in claim 1 wherein,said actuating means includes first andsecond stationary electrical contacts and a movable electrical contactwhich is movable concurrently with said overriding throttle closingmeans, said movable contact being sequentially engaged with said firstcontact, neither of said contacts and then with said second contact whenthe overriding throttle limiting means moves from wide open throttleposition to close throttle position, said first contact being connectedwith said circuit means for causing it to energize the motor for highspeed operation when said first contact is engaged by said movablecontact and for causing it to energize the motor for low speed operationwhen said first contact is disengaged by said movable contact, saidsecond contact being connected with said circuit means for causing it tostop the motor when said second contact is engaged by said movablecontacts, said circuit means being operative to reversibly energize saidmotor at said slow speed in accordance with changes in said speedsignal.
 3. The invention as defined in claim 2 wherein,said circuitmeans includes means for deenergizing the motor when the movable contactmoves from said second contact to said first contact when the enginespeed is less than a predetermined governed value, said circuit meansbeing operative to energize the motor in the close throttle direction atsaid slow speed when the engine speed exceeds the governed value.
 4. Theinvention as defined in claim 2 wherein,said circuit means includesmeans for energizing the motor at said high speed in the open throttledirection when the engine speed is less than a predetermined precallvalue.
 5. The invention as defined in claim 1 wherein movement of saidoverriding throttle closing means from wide open throttle to closethrottle would require about three seconds at said high speed and wouldrequire at least eight seconds at said low speed.
 6. The invention asdefined in claim 1 wherein movement of said overriding throttle closingmeans from wide open throttle to close throttle would require about 20to 25 seconds at said low speed.